In response to PAR-15-085, the University of Pennsylvania and Princeton University have assembled an interdisciplinary team of bioengineers, computational scientists, trauma surgeons, and hematologists to develop a multiscale model of trauma. Better elucidation and quantitative measurement of blood reactions, platelet signaling, neutrophil signaling, and endothelial signaling pathways under hemodynamic conditions are directed at clinical needs in: (i) stratifying trauma induced coagulopathy (TIC) risks, (ii) improving the safety and efficacy of transfusion therapy, and (iii) identifying moleculr mechanisms that can be targeted pharmacologically or serve as improved biomarkers. Six specific aims are proposed: Aims 1 and 2 focus on the development of mechanistic and data-driven computer models of biochemical and cellular function relating to: protease cascades of coagulation, fibrinolysis, and complement assembly, as well as platelet, neutrophil and endothelial function. Aim 3 then develops a multiscale model of blood clotting and hemostatic function in a damaged blood vessel. The individual sub-models at the single cell level are combined into the unit vessel bleeding model which is related closely to laboratory experiments that test the functional performance of mouse and human patient blood under the extreme conditions of trauma. Aim 3 also involves microfluidic bleeding assays of human blood under diverse pathological conditions that explore bleeding scenarios involving combinatorial alterations of biochemistry and biology relevant to trauma. Aim 4 will implement coarse projective integration (CPI) to make prediction of the evolving systemic circulation and its interaction with a traumatized tissue where bleeding is quantified at the single cell to single vessel to tissue scale. These simulations are designed to validate an in silico trauma patient in order to stratify the risk of TIC. In Aim 5, the intensive use of fresh blood samples from trauma patients and annotated records from trauma patients will be part of the validation of the multiscale CPI algorithm. Key preliminary data demonstrates detection and quantification of platelet hypofunction in trauma patients. Aim 6 will utilize a novel in vivo mouse injury model to study bleeding and hemostasis in a calibrated model of trauma severity. This in vivo data will also be used to enhance the predictive capability of the multiscale model and to potentially identify biomarkers for stratifying TIC risks in humans. Also the mouse work emphasizes the use of novel fluorescent sensors developed specifically for this research. Overall, these aims represent the full integration of platelet, neutrophil, and endothelial signaling models with realistic and hierarchical hemodynamic/mass transport simulations that regulate bleeding and blood function at the various scales relevant to trauma.